Remote control apparatus for electric tuning systems



May 25, 1937.

A. A. THOMAS 2,081,686

REMOTE CONTROL APPARATUS FOR ELECTRIC TUNING SYSTEMS 6 Sheets-Sheet 1 Filed July 19, 1928 INVENTOR May 25, 1937. A. A. THOMAS REMOTE CONTROL APPARATUS FOR ELECTRIC TUNING SYSTEMS Filed July 19, 1928 6 Sheets-Sheet? INVENTOR y ,1937. I A. A. THOMAS y 2,081,686

REMOTE CONTROL APPARATUS FOR ELECTRIC TUNING SYSTEMS Filed July l 9, 1928 6 SReets-Sheet 3 INVENTOR May 25, 1937,, A. A. THOMAS 2,031,535

REMOTE CONTROL APPARATUS FOR ELECTRIC TUNING SYSTEMS Filed July 19, 1928 i 6 Sheets-Sheet 4 Z INVENTOR May 25, 1937. A. A. THOMAS 2,081,636

REMOTE CONTROL APPARATUS FOR. ELECTRIC TUNING SYSTEMS Filed July 19, 1928 -6 Sheets-Sheet 5 VINVENTOR Pa'tented- May as, 1937 Y rumors coN'raor. .APIARATUS" FOR I nmcrmc TUNING srs'rsms Adolph A. Thomas, New York, N. r., assignor to Radio Corporation of America. New York, N. Y. a corporation of Delaware Application July 19, 1928, Serial No. 293,861

37 Claims.

This invention relates to the art of broadcast reception, and its object is to provide novel means for electrically adjusting the tuning niechanismof a radio set at a distance to bring in any one of a number of selected stations. In a preferred form of my invention, I employ a control box or cabinet having a series of keys, or other handoperable members, each representing a certain broadcasting station as chosen by the manufacturer or the owner of the apparatus. This control box may be at any distance from the radio set, and the desired station is brought in by simply pushing down the corresponding key. No other manual operation is necessary. Ihe mere depression of a key, or whatever form of handoperable member is used, automatically controls electromagnetic connections which turn the tuning shaft (or shafts) of the radio set the right amount. The control apparatus requires no attention when changing from one station to am-- 'j other, except actuating the selected key. Furthermore, the tuning shaft is always free to be operated by hand in the usual way independently of the remote control connections. This enables a person to bring in stations not represented by tical examples of remote control apparatus embodying my invention. I shall describe these illustrative embodiments in detail, so that those skilled in the art may fully understand this invention and put the same to practical use. In these drawings- Fig. l is'a perspective view of a radio receiver provided with my automatic tuning attachment,

the control box being remote from the receiver and electrically. connected thereto by conductors in the form of a single cable;

Fig. 2 shows an inside plan view of that portion of the radio receiver which contains the mecha nism for operating the condenser shaft;

Fig. 3 illustrates the control box in plan, the cover being partly broken away to disclose certain parts inside;

Fig.4 is a transverse section on-line H of Fig. 3, with one of the keys and-its associated switches in; normal position; Fig. 5, which is like Fig. 4, shows the-key fully depressed to close the switches that control certain circuits. as will later be described; Fig. 6 is similar to Figs. 4 and 5. and shows the depressed key locked against return movement,

the associated switches being open;

Fig. '7 is an enlarged sectional detail of the head of a key provided with a removable disk which carries notations identifying a certain broadcasting station;

Fig. 8 is an enlarged sectional detail of one of the illuminated windows in the control box;

Fig. 9 shows in section a cap adapted to be emovably fitted over a key head or a window of are control box for identifying a selected station;

- Fig. 10 is a front view of the controlbompartly in section to reveal the inside mechanism;

Fig. 11 represents a transverse section on line 11- of Fig. 2, showing the electromagnetic mechanism that operates and controls the tuning shaft when a key is actuated;

.Figs. 12 and 13 are detail views on lines I2-l2 and l3-l3 of Fig. 2 to show the arrangement for automatically returning the tuning shaft to normal position when the main switch in the control box is opened; 1

Fig. 14 is a diagram of the circuit connections between the control box and the electromagnetic mechanism that operates the tuning shaft, it being understood that this diagram is based on the mechanical views of the preceding figures;

Fig. 15 illustrates, in a diagrammatic way, a modification in which the tuning shaft is connected to an electric motor through a magnetic clutch controlled by the keys of the control box;

Fig. 16 is a diagram showing a parallel arrangement of switches that. control the magnetic clutch embodied in Fig. 15;

Figs. 1'7 and 18 are details of certain switches included in Fig. 15 for controlling the clutch circuit, Fig. 1'7 showing the switch in normal closed position, and Fig. 18 showing the switch opened by the associated arm on the condenser shaft;

Fig. 19 illustrates diagrammatically another 1 modification in which an electric motor is connected to the tuning shaft through a slip-clutch arrangement;

Figs. 20mm 21 are detail views at right angles to each other, partly in section, showing an adjustable mounting of the radial stop arms on the tuning shaft;

. Fig. 22 is a detail showing how the radial stop arms or projections on the tuning shaft are automatically locked tothe associated key-controlledstops; and

I Fig. .23 is a sectional detail of a key provided with a head that contains a lamp for illuminating the cap of the key.

Before taking up a detailed description of the drawings, I wish to explain that the parts in the mechanical views have been purposely spread out for clearness, and their relative proportions have actual mechanism can be made more compact than the drawings indicate. It will therefore be understood that the illustrations about to be de- ":ribed are not to be taken as shop drawings made to accurate scale.

Referring to Fig. 1, the cabinet R represents a radio-receiving set of any approved construction and design, the details of which need not'be shown or described. In the right-hand portion of the radio cabinet R is housed the electromag netic mechanism which operates the tuning shaft to bring in a selected station, as will be fully explained in due course. The front panel In of radio receiver R has a tuning knob l2 for manually turning the condenser shaft (or shafts) to bring in a desired station. It is not necessary to show any driving connections between the knob l2 and the condenser shaft, because such connections are well known and are to be found in all the radio receivers available in the market. A suitable dial [3 indicates the correct position of the condenser shaft for any selected station. A knob ll regulates the volume of reproduction, and a switch [5 closes and opens the main operating circuit of the set, which may be connected to a battery or to a house lighting circuit.

The automatic tuning mechanism of radio re ceiver R is' electrically connected by a cable 15 to a control box, indicated as a whole by K, which may be placed at any distance from the receiver. The cable 16 is supposed to contain all the conductors required to effect the necessary circuit connections between the control box and the tuning mechanism housed in the radio cabinet. The control box K has a set of manually operated members marked A, B, C, D andE, which are shown in the form of depressible keys, but which may be in the form. of push buttons, snap-over levers, and the like. For brevity, however, I shall refer to the parts A-E as keys. It has been assumed here that the radio set has an automatic tuning range for five stations selected by the owner or maker of the receiver, and so there are five keys in the control box, each key representing one of the selected stations. The operative connections between the control, box K and the radio set R are such that the .mere depression of a key automatically tunes in the corresponding station. A knob IT on the control box enables the operator to regulate the volume of reproduction, and a switch It throws the radio set into and out of circuit with the batteries or house lighting circuit. In other words, the knob I! and switch 18 on the control box K perform the same functions as the knob l4 and switch IS on the radio cabinet R. For this purpose, the electric connections controlled by the parts l4 and i5 may be arranged in parallel with the connections con-- trolled by the parts I! and I8. It will not be necessary to show any circuit connections by which the radio set is throvm into and out of circuit, nor any connections for regulating the volume, because such matters are well understood in the radio art. For instance, the knobs i4 and I1 may control, each independently of the other, a variable resistance shunted across the second-- ary of the first audio transformer, as will be understood without further explanation. The control box K is preferably provided with windows I9, one for each key, and these windows may have marked thereonthe names or call letters of the selected stations. When a key is pushed down to bring in the desired station, a lamp circuit is automatically closed and the corbeen exaggerated for the same reason. The

responding window is lighted to inform the operator that the station has been tuned in. The window remains lighted during the operation of the receiver, and thereby informs the operator (or anybody looking at the control box) which particular station is on the air.

Having now described in a general way the manner in which my invention is used to tune a radio receiver from a distance by merely operating a key, I shall now take up a detailed description of the various mechanisms for accomplishing the results mentioned. I shall first explain what is inside the control boxK, and for this purpose I shall refer to Figs. 340. The keys A-E being of identical construction, a description of one will suffice for all. Each key comprises a shank 20 provided with arecess 2!, a hump or cam projection 22, and a lateral offset 23. For

convenience of manufacture, the shanks 20 can be punched from sheet metal. It will simplify 'the description if I use the reference numeral 2|) to indicate the keys generally, and the letters A-E shall be used when a particular key is to be identified. Referring to Fig. 7, each key 20 has a head ill, which is riveted in place or otherwise rigidly attached. The head 24 is a cup-shaped member of sheet metal and carries a disk 25 on which a selected station is identified, as will be seen in Fig. 3. The disk 25, which may be a piece of paper, celluloid, fiber, or other material suitable for receiving notations, is removably mounted on the key head 24 by a cap 26 adapted to be forced over the same. The cap 26 may be sheet metal, celluloid, fiber, vulcanized rubber, or any other suitable material having sufficient resiliency to grip the head 24 in a tight and yet releasable frictional engagement. Instead of using a separate disk 25, which shows through the center opening of cap 26, these two parts may be combined in a single member, as shown at 21 in Fig. 9. The cap 27 has an integral top 28, which serves the same purpose as the disk 25 of Fig. '7.

The keys 2d are supported and guided for vertical movement in a bar 29, which is suitably attached at its ends to the sides fill oi the control box. The bar 29 is here shown as a channel bar shaped from sheet metal and provided at each end with extensions 3! bent downwardly to receive fastening members 32, as best shown at the right of Fig. 10. The keys 20 pass through transverse slots 33 in bar 29, and the parallel upright sides of the bar act like guide members for the keys in their down and up movement. Additional guiding means for the keys 20 is afforded by the top 34 of the control box, this top being provided with slots 35 through which the fiat shanks 20 of the keys pass in a close fit, but sufficiently loose for free movement.

A rod or shaft 36 is supported at its ends in a pair ofbrackets or bearing hubs 31 secured to the sides 30 of the control box K, and on this shaft are mounted rotatable sleeves 38, each of which carries a lever 39. The sleeves 3B are independently movable and hold the levers 39 in properly spaced relation on shaft 35. Each lever 39 is provided at its front end with a slot 40 adapted to receive a pin 4! carried by the associated key 20, whereby the downward movement of a key throws the rear end of the connected lever upward, and vice versa. As seen in Fig. 10, the levers 39 are connected to the lateral offsets 23 of the keys, so that the keys and levers may be arranged in alignment. This, however, is not the main purpose of the lateral offsets 23 of keys 20, as will be understood later on. Back of the transverse shaft 38 is a fixed rod 42 supported at its ends in brackets 43, which are attached to the sides 38 of the control box in any practical way. A contracting coil spring 44 is connected at 45 to the rear section of each lever 89, and the lower end of the spring is connected at 48 to the bottom 41 of the control box. The springs 44 normally hold the rear end of levers 89 against the fixed stop bar 42, as shown in Fig. 4. This means that the keys 28 are normally held in raised or uppermost position by the tension springs 44.

A. bar 48 is mounted betweenthe sides 38 of control box K, as by means of brackets. 48 or otherwise. A series of switch arms 50 of curved spring metal are attached at their lower ends to the cross-bar 48 and spaced in alignment with the pivoted levers 39, as will be understood from Fig. 10. Each switch arm 58. has a cam portion arranged to be engaged by the rear end of lever 39 when the latter is rocked upward on depression of a key. By comparing Figs. 4 and 5, it will be seen that, when the rear end of lever 38 is raised, the associated switch arm 58 is forced rearward at its upper end into contact with a conducting bar 52, which is supported on brackets 53 or otherwise between the sides 30 of the control box. The bar 52- may be formed as'a channel bar of thin sheet metal, such asbrass. The bars 48 and 52, which can be mounted on a. single frame or on one pair of brackets, are connected in circuit and serve as common terminals for the individual switch arms 58. It is assumed that the control box K is of insulating material, like wood, bakelite, and so on. If the box is made of metal, the bars 48 and 52 must be insulated from each other. In Fig. 10, conductors 54 and 55 are connected to the bars 48 and 52, respectively. When any one of the switch arms 50 is moved into contact with bar 52, the latter is electrically connected with bar 48. In other words, the fixed bars 48 and 52 and the movable spring arms 50, which are arranged in parallel between the bars, constitute a normally open switch adapted to be closed when any key is depressed.

A cross-bar 58 mounted on brackets 51 between the sides of the control box carries a series of switch arms 58 arranged in line with the keys 20. The switch arms 58 are in the form of spring fingers having a. rearwardly extending cam portion 58 arranged to be engaged by the projection 22 of the associated key when the latter is depressed. If the bar 58 is of metal, it is necessary to insulate the spring fingers 58 from each other. The upper end of each spring finger 58 is in the form of an extension 80 (see Fig. 4)

for attaching a conductor. An L-shaped bar 8!.

58 ofthe associated spring finger 58 and forces the latter into contact with the conducting strip 82, as shown in Fig. 5.

Attention is called to the fact that when a key is pushed down, the spring member 58 is closed in advance of the switch member 58.: 'This will be understood by reference to Fig. 4, where the dotted outline 28 indicates the position of a key when depressed sumciently to close the switch The spring fingers 58. are

member 58 while the switch member 58 is still open. The dotted outline 38' indicates approximately the position of the rear end of lever 89 when the key has been depressed to the position lndicated'at 20'. The switch members 58 are so shaped that the cam portion 5! is forced rearward by the actuated lever 38 only after the associated switch member 58 has been moved into contact with the conducting strip 83. The object of closing the switch member 58 ahead of the switch member 50 whenever a key is pushed down, will be explained when I describe the electromagnetic mechanism for actuating the tuning shaft in accordance with the depressed key to bring in'the selected station.

A contact bar 88 is mounted on an insulating strip 81 in vertical alignment with the keys 20, The supporting strip 81 is secured to the base 41 of the control box. A second bar 88 is mounted to the rear of bar 88 on a suitable insulating support 89. The supports 8|, 81, and 88 can easily be made as one member, either as a casting, or a sheet metal stamping, or as a frame molded from. bakelite or like material. If this member is of metal, the supported contact bars 83, 88, and 68 will obviously have to be insulated. It is.

' evident from Figs. 4, 5,and 6 that the five contact bars 48, 52, 83, 88, and 88 may be attached to a singleL-shaped frame inserted as a unit intothe control box after the switch parts have been mounted on the frame. This facilitates the work of assembly. Spring fingers are fixed at their rear ends on the common conducting bar. 7

88, and the front ends of these fingers extend beneath the keys 20. The spring fingers 18 are normally by their inherent tension out of contact with bar 86. When a key 20 is fully depressed, as shown in Fig. 5, the associated switch arm III is pushed down into contact with bar 88, whereby the latter becomes electrically connected with bar 68. It should be noticed that the switch member 10 is notclosed unless and untilthe key is pushed down to its fullest extent, which occurs after the switch member 59 has been moved into contact with bar 83, as previously explained. The spring fingers l8 constitute a series of normally open connections arranged in parallel between the bars 88 and 68, so that the switch constituted by the members 88, 88, and 10, is closed whenever any one of the spring fingers I8 is moved into contact with bar 88.

When a key is pushed down, it is automatically locked against full return movement by a bar H 'slidably mounted on supports 12, which may be a pair of posts secured to the base of the control box by screws or bolts 13, as may be seen in Fig. 10. The bolts 13 pass through longitudinal slots 14 in bar II to permit movement of the bar transversely of the control box for locking and releasing the keys. The bar H is provided with lateral slots 15, one for each key: When the bar H is in normal position, the slots 15 are in alignment with'the lower ends of keys 20, as

shown in Fig. 10. -Therei'ore, when a key is depressed, its lower end passes through the aligned slot 15 of bar Ii. When the bar H is shifted to the left from the position shown in Figs. 3 and 10,

the slots 15 are moved out of alignment with the keys 20, so that the keys are locked in normal raised position, with the exception of the depressed key which is locked by the bar against return movement. This will be understood from Figs. 5 and 6. Fig. 5 shows one of the keys 28 in fully depressed position. As will be presently explained, when the switch 10 is closed, certain electromagnetic mechanism is energized to move the bar II to locking position. when the depressed key is released, it can only move up a slight distance-that is to say, until the shoulder 16 of recess 2| strikes the bottom of bar ll. The purpose of allowing a slight upward movement of the depressed key, before it is locked by the bar H is to open the switches 50, 58, and 10 to prevent waste of current. This practical advantage will be fully appreciated when the operation of the apparatus is described.

The key-locking bar II is operated by a bellcrank or right-angled lever 11 pivoted at I8 on a post I9 projecting upwardly from the base of the control box. One end of bar II carries a pin 80 which extends through a slot 8i in the bellcrank 11. The short arm of this bellcrank carries an armature 82 arranged to project between a pair of electromagnets B3 and 84, which are mounted on brackets secured to the bottom of the control box. For brevity I shall refer to the electromagnets 83-and 84 as coils, it being understood that these coils are provided with magnetic cores to concentrate the flux which acts upon the armature 82. It is evident from Fig. 3 that, when coil 83 is energized, the bellerank I1 is rocked into the dotted line position 11, and the bar II is shifted to the left into locking position. When the other coil B4 is energized, the bellcrank TI is moved back to normal position and pulls the bar 11 to the right until the slots 15 are in line with the keys. Whenever the bar H is moved from looking to releasing position, the previously depressed key (see Fig. 6) automatically snaps up to normal position under the action of spring 44.

To summarize the action of the locking bar ll: whenever a key is fully depressed, the switch arm 10 closes the circuit through coil 83, which actuates the bellcrank Tl to move the bar ll into locking position, so that the raised keys cannot now be pushed down. This prevents in terference with the operation of the automatic tuning mechanism after a key is pushed down to bring in a selected station. When the depressed key is released by the operator, it moves up slightly (compare Figs. 5 and 6) and is locked in this intermediate position by the bar ii. The depressed key also indicates to the operator which station has been tuned in, independently of the lighted window 19, to which reference was made in connection with Fig. 1. The restoring coil 84 is energized to return the locking bar H to normal position when the main switch 18 is thrown open or to off position, as will later be fully described.

As previously mentioned, the control box K is provided on top with a series of windows l9 arranged back of the keys. The structural details of these windows are shown in the enlarged view of Fig. 8. Each window is formed by a cylindrical extension 86, which is covered by a disk 81 held in place by a spring cap 88. If the cover 34 of the box is made of sheet metal, the window extensions 85 can be stamped or punched out as integral projections of the cover. The disks 81 may be of paper, celluloid, or any transparent or translucent material adapted to receive writing for indicating thereon the station represented by the associated key. This is illustrated in Fig. 3. The cap 88, whichhas a circular hole for dis- Consequently,

playing the disk 81, may be stamped from sheet metal, celluloid, rubber, or any other material adapted to engage the window projection 88 in a tight frictional engagement that permits removal of the cap. Instead of making the disk 81 separate from the cap 88, these two parts may be formed as a single member, similar to the key cap 21 in Fig. 9. Behind each window I! is a lamp 89 mounted on a shelf 9i), which may simply be an L-shaped bar of sheet metal attached to the inside of the cover 34, as shown in Figs. 4, 5, and 6. The sockets iii of the lamps are mounted on shelf 90, and conductors 92 connect each socket in circuit, so that the lamps can be controlled individually by the associated key, as will later be explained. The light-transmitting disks 81 may be differently colored to heighten the optical effect, especially if the control box is in the dark. Also, the use of selected colors for the windows serves as an additional means for identifying the various stations.

The next thing to describe is the electromagnetic mechanism mounted in the radio cabinet R for actuating the tuning shaft by merely pushing down one of the keys A-E of the control box. This mechanism is shown in Figs. 2 and 11--l3, to which I shall now refer. The radio receiving apparatus in the cabinet R has a rotary condenser shaft 93 for adjusting one or more com densers 94. Only one of these condensers is shown in Fig. 2, but it will be understood that the shaft 93 operates as many condensers and other tuning devices as are necessary in any particular radio receiver to bring in a desired station. In other words, the rotary shaft 93 is to be regarded as representing broadly any type or construction of tuning means for a radio receiver. At the present time the most popular style of radio set has only a single tuning knob which operates a gang of condensers. The radio set illustrated in Fig. 1 may be assumed to be of that type, so

that the knob i2 is operatively connected to the tuning shaft 93 to adjust the same by hand when desired.

The condenser shaft 93 is supported in sultable bearings, one of which is'shown at 95 in Fig. 2, and the shaft carries a series of radial arms 95. one for each key A-E of the control box. The arms 86 are in predetermined angular relation to each other, each arm representing a selected station. The angular position of each arm 95 depends upon the position which the condenser shaft must occupy to bring in the station represented by that arm. It is desirable that the arms 96, while rigidly mounted on the condenser shaft 93, should be adjustable radially thereon, so that a particular radio receiver can easily be callbrated in the factory and by the owner for certain selected stations. Figs. 20 and 21 show a novel mounting to permit easy adjustment of the radial arms 95; Since the mountings for all arms are the same, a detailed description of Figs. 20--21 is supposed to apply to all the radial arms 96. Each arm has a housing 91 formed with side slots 98 to permit mounting of the housing on shaft 93. The housing 91 encloses a worm gear 95 hired on shaft 93 by pin IOU or otherwise. A worm shaft H is rotatably mounted in housing 9! and is permanently in mesh with worm gear 95. A knurled knob I02 at one end of worm shaft IOI permits easy rotation of the latter in either direction. The rounded ends 18' of slots 98 act like rotary bearings and hold the housing 91 firmly seated on shaft 93. It is clear from Fig. 20 that rotary adjustment of the'worm shaft IOI causes corresponding radial adjustment of the arm 98 on shaft 93; The connection between gear 99 and worm gear IOI permitsadjustments of micrometer fineness and is such that the arm 96 is always looked rigidly to the tuning shaft, In other words, when the arm 96 has been adjusted to the desired angular posi-'- tion on shaft 93 by turning the knob I02 one way or the other, the arm 96 is automatically locked in adjusted position without attention by the op erator. It is understood that the engagement between the teeth of gear 99 and the worm thread on shaft I ispractically free from loose play. The arm 96 and housing 91 can be cast as a single piece, preferably from aluminum or alu minum alloy, which is light and strong.

Referring to Fig. 2, there is a sleeve or hub I03 projecting horizontally from the side wall MI of the radio cabinet 13.. The sleeve I03 is formed with a base or enlargement I05 adapted to receive screws or bolts for securing the sleeve rigidly in place. A rotary shaft I06 (see Fig. 11) is mounted in sleeve I03 and the outer end of this shaft carries a pair of gear wheels I01 and I09, which may be cast as a single member or secured together as two separate parts. The small gear I 01 meshes with a reciprocable rack bar I09 connected at its ends to a pair of magnetic cores III? and H2, which are operatively associated with coil H3 and Ill, respectively. Each coil and its movable magnetic core constitute a solenoid. Since the cores H0 and I I2 are always supported in the center openings of coils H3 and Ill, no separate support is necessary for the rack bar I09 to hold it constantly in that, when the coil H3 is energized, the core I I0 is pulled in and the rack bar I09 is moved to the left, whereby the gears I01 and I08 are retated clockwise. Conversely, when the coil Ill is energized to pull in its core II2, the rack bar I09 is pulled to the right and the gears I01 and I08 are turned the other way. The coils H3 and II are rigidly held in axial alignment by any practical form of mounting. In Fig. 11, I have shown a pair of L-shaped brackets II1 to which the coils are connected. The brackets II1 are preferably non-magnetic and may be secured to the bottom of the radio cabinet.

The large gear ,wheel I08 has a peripheral section II8 which has no teeth and may therefore be called an inoperative section. The teeth of gear I08 are adapted to engage the teeth of a small gear II9 fixed on the condenser shaft 93. An arm I20 on shaft 93 'is arranged to engage a fixed stop I2I for holding the shaft in normal 5 or neutral position. The arm or projection I20 is rigidly mounted on shaft 93, but radial adjustment of the arm is permitted by a set-screw I22. The stop I2I may be in the form of an L-shaped bracket secured to the side I00 of the radio cabinet, as shown in Fig. 2. At one end.

of the toothless or inoperative section I I8 of gear wheel I08 is a projection I23 normally engaging a fixed stop I24, which is carried by a post I25 attached to the bottom of the cabinet. When the tooth or projection I23 strikes the stop I24, the

counter-clockwise movement.

large gear I08 has reached the limit of its This position of gear I08 may be called its normal or inoperative position, because its teeth are then out of engagement with the small gear II9 on shaft 93. It is evident, therefore, that when the large gear I08- is in normal position (or in other words, when the control box K is not in use), the condenser shaft 93 is free to be operated by the hand knob I2 (see Fig. l) to bring in any desired station independently of the control box. This feature is of practical advantage, because it leaves the radio set always in condition to be tuned by hand in the usual way, the same as if the control box K and the associated operating mechanisms were absent.

e The projection I23 on gear wheel I08 is normally held against the fixed stop I24 by a contracting coil spring I26, one end of which is attached to a pin- I21 projecting laterally from the gear, as shown in Fig. 2. The lower end of spring I26 is attached to the bottom of the cabi- I net at I28 in any practical way. The connecting points I21 and I28 of spring I26 are such that normally the line of pull of the spring is to the left of shaft I06, so that the tension of the spring holds the projection I23 firmly against the stop I24. When the coil H3 is energized to turn the gear I08 clockwise, the tensioned spring assists the action of the coil as soon as the connecting point I21 crosses the neutral line I29. In other words, as soon as the axis of spring I26 moves to the right of the imaginary line I29, the

spring pulls the gear wheel I 08 clockwise independently of coil II3. This assures the complete movement of gear I 08 and the connected parts, even if the coil II3 should be de-energized prematurely by release of the depressed key.

Assuming the parts to be in normal position, as illustrated in Fig. 11, it will be seen that when the operating coil H3 is energized by pushing down a key, the large gear I08 is rotated clockwise and moves into mesh with the small gear I I9 on condenser shaft 93, so that the latter is rotated counter-clockwise to throwthe radial arms 96 forward. The transmission ratio between the rack bar I09 and the gear wheel H9 is such that the linear movement of the bar produces sufficient rotation of condenser shaft 93 to tune in any one of the stations represented by the arms 96. In the present instance, it has been assumed that the maximum movement of the condenser shaft is 180 degrees, or half a revolution. If the radio receiver is such that its tuning shaft requires a complete revolution to adjust the condenser or condensers from minimum to maximum capacity, it is a simple matter to arrange the driving connections for shaft 93 so that the maximum movement of rack bar I09 will produce one revolution of the tuning shaft.

The movements of condenser shaft 93 are controlled by a series of adjustable stops I30 adapted to be moved into and out of the path of travel of the radial arms 96, which are in alignment with the stops, as seen in Fig. 2. In the present embodiment, the stops I30 are in the form of slidable'bars, each of which is pivoted at I3I to the lower end of a lever I32 (see Fig. 11). These levers are pivoted for independent movement on a rod I33 carried by a pair of arms I34, which extend rearward from a suitable frame I35 rigidly supported in the radio cabinet. Sleeves or bushings I36 on rod I33 hold the levers I 32 properly spaced, aswill be clear from Fig. 2. Each lever I32 carries an armature I31 arranged to extend between a pair of coils I38 and I39. The armatures I31 extend substantially at right angles to the levers I32, so that each lever and its connected armature constitute a bellcrank pivoted at its apex on the common supporting rod I33. Each lever and its armature canbe cast as a unit from magnetic metal, or they can be stamped-or punched out from magnetic sheet metal as a single piece. If desired, however, the levers I32 may be formed of nonmagnetic material separate from the armatures I31 and operatlvely connected thereto in any practical way. The coils I38 and I39 are supported onv brackets I40 projecting from the frame I35. A spring finger MI is associated with each armature I31 to hold the same in lower and upper position against (or close to) the magnetic core of coil I39 and coil. I39. For thlspurpose, the spring ringer MI has a bevelled or cam-shaped projection M2 arranged to engage the free end. of armature I31. The spring finger MI is sufficiently resilient to be pushed out of the way by the arr-nature as the latter moves from one position to the other. But after the armature has reached upper or lower position, the projection I42 of spring arm MI holds the armature firmly in place. The purpose of this arrangement is to hold the slidable stops I30 either in normal withdrawn position. or in their operative position when projecting into the path of the radial arms 96 on tuning s' ments between a pair of spaced rods H3, which are mounted at their ends in arms M4 at the supporting frame I35, as shown in Figs. 2 and 11.

The stops I30 are normally withdrawn, so as to be out of the path of the radial arms 96 on shaft 93, as will be clear from Fig. 11, Where the dotted circle 96 represents the path of the arms. When one of the coils I38 is energized (through connections that will later be explained), the associated armature I3! is pulled down and the lever I32 is rocked rearward to throw the connected stop I30 into the path of the aligned arm 96. In Fig. 2, the dotted outline I30 indicates roughly the operative position of one of the stops I30. It is clear that, when a particular stop is moved rearward, the rotation of condenser shaft 93 is interrupted the moment one of the arms strikes the operative stop. The rods H3 at the free end of each stop bar I30 cooperate with the pivot hearings Ill and I33 to hold the bar rigid when the arm strikes it, so that the shaft 93 is definitely stopped in correct tuning position. lilthough the stops I30 are arranged in horizontal alignment, the amount of movement of the tuning shaft 93 depends upon the particular stop that is moved to operative position, this movement being predetermined by the angular position of the particular radial arm 98 that ters the operative stop. It pposed that 96 are so arranged on condenser or conden pacity' values required or the selected Each stop I30 is controlled by one oil AE of control box K. Consequently, y pushing down the key that represents the station, the operator automatically sets up corresponding stop I30. Only one stop is set up at a. time, because it is supposed that the operator will push down only one; key. As previously explained, after one key has been actuated, the other keys are automatically locked,- so that there is no danger of a second stop I30 being set up while the first stop is still in operative position. Since the coils I38 throw the stops I30 rearward into operative position, I shall call them the setting-up coils. The coils I39 may be termed the restoring coils, because they withdraw the stops I30 to normal inoperative position.

' In the particular embodiment of the operating mechanism illustrated in Figs. 2 and 11, it is desirable to provide means for compelling the condenser shaft 93 to be in normal position when the radio set is tuned from the remote the control box to bring in a certain station,

the condenser shaft would not be actuated by the electromagnetic mechanism to proper posh tion. Since radial arrangement of the arms 96 on shaft 93 presupposes that this shaft will always start from the same position, it it that the condenser shaft must always be in the same position when the large gear I00 moves into engagement with the small gear H9. ifnerefore, to assure the proper operation of the r mote control mechanism without regard to position in which the condenser shaft may e been left after a manual tuning of the reprovide means for automatically reing the condenser shaft to normal position re the coil t" I shall describe this automatic restoring mechanism, which is best shown in Figs. 2, l2, and iii.

The condenser shaft 93 carries a pinion I45 adapted to mesh permanently with a rack bar 146, which is attached to or otherwise connected with) a-solenoid core Ill associated with a magnetizing coil I49. The rack bar I40 is held in engagement with the teeth of pinion I" by a supporting and guiding bracket 9, which may conveniently be secured to the bottom I I6 of the radio cabinet. The coil I48 is mounted on a post or bracket I50 projecting upwardly from the base of the cabinet, or otherwise supported. A ring I5! of insulating material is sup ported on brackets I52 in concentric relation to the condenser shaft 93. Two circular conducting strips I53 are embedded in or otherwise secured to the inside of ring I5I, which may be molded of bakelite or other insulating material. The contact strips I 53, which may be shaped from strips ofbrass, are arranged diametrically opposite. being separated by the'insulating material of ring [St at points I54. A switch arm I55 fixed on condenser shaft 93 rotates inside the in normal position (that is, with the projection 0 I20 engaging the stop I2I as illustrated in Fig. 11), the switch arm I55 is out of contact with both conducting strips I53, as will be clear from Fig. 12. However, when the condenser shaft is out of normal position, the switch arm I55 engages the strips I53 and thereby closes the cirl is energized to rotate the cuit through coil I48. These circuit connections will presently be explained in the description of Fig. 14. When the coil I48 is energized, the rack bar I46 is drawn forward (to the left, as viewed in Fig. 13), and the condenser shaft 93 is turned rearward until the projection I20 strikes the stop I2 I, whereby the shaft is restored to normal position. when this occurs, the switch arm I is out of contact with strips I53, and the circuit through coil I48 is automatically interrupted. A pair of binding posts I56 on ring I5I permit circuit conductors to be readily attached to the contact strips I53. I

The circuit connections for the electromagnetic mechanisms above described are diagrammatically indicated in Fig. 14. To promote clearness in this drawing, the mechanical parts are illustrated by diagrammatic outlines and have been purposely spread apart to prevent confusion of lines. The main switch I8 is shown as a toggle lever pivoted at I59 in the control box and extending out of the box through a slot I60, which also serves' to limit the movements of the switch to "on and off" position. The lower end I of switch lever I8 engages a cam projection or rounded hump I62 on a spring finger I63, the normal tendency of which is to press against the lever and hold it in on" and off position. The spring finger I63 is connected by insulating posts or blocks I64 to the free ends of similar spring fingers I65 and I66. Contact arms I61, I66, and I69 are'associated with the spring fingers I63, I65, and I66, respectively, to form three switches adapted to be simultaneously opened and closed by the toggle lever I8. A lateral extension I10; on lever I8 controls a switch represented by a pair of normally open spring contacts I1 I. Conductors I12 connected to switch I1I lead to the radio receiver R. for closing its'supply circuit or circuits, such as the filament circuits, rectifier circuits, etc. The switch I is arranged in'parallel with the main switch I5 of radio receiver R. a

so that the closing of either switch puts the set in operative condition. It should be noted that the switch arms I63, I65, and I66 are open in either position of the toggle switch lever I8, but these switches are closed by being pushed down against'contact arms I61, I68, and I69, respectively, when the lower end of the lever rides over the highest portion of the hump or cam I62 on spring arm I63. The purpose in leaving the switches open when the arm 18 is in on and "011 position is to prevent waste of current, as will more clearly appear later on. The switch .I1 I, however, remains closed as long as the toggle lever I8 is in on position. The hump or cam I62 is so shaped that the switch arms I63, I65,

and I66 remain closed long enough during the throw-over movement of lever I8 to allow the associated electromagnetic devices to perform their intended functions.

In Fig. 14, it has been assumed that the source of current supply is the house-lighting circuit, to which connection. is made by simply inserting a plug I13. If the lighting circuit is fed by alternating current, it will be necessary to use a rectifier, of which several types are available in the market. The outline I14 represents a suitable form' of current rectifier. Of course, the leads I15 and I16 may be connected to a battery or other source' of direct current having the required voltage and amperage for properly operating the various electromagnetic devices previously described. One end of the operating coil III is connected by conductor 64 to the common contact bar 48, which is here represented by a line. It will be remembered (see Figs. 4 and 10) that the bar '46 serves as a common support for the individual switches 50. This mounting is shown diagrammatically in Fig. 14 by connecting wires 48. The other end of coil II3 is connected by wires I11 and I18 to the supply conductor I15. I might as well explain at this point that, when I refer to any of the connections in Fig. 14 and the other diagrams as wires, I use this term in its broadest possible sense to indicate any practical form of electrical connection, whether made by wires, strips, bars, plates, or other means. To facilitate the description of Fig. 14, the key-operated switches 50 are differentiated by the suffix let ters a-e, which correspond to the key letters A-E. In other words, when key A is pushed down, it closes switch 50a; key B closes switch 50b; and keys C, D, and E close, respectively,

switches 50c, 56d, and 56e. In the same manner I have distinguished the switches 56 and 16, the arms 96 on shaft 93, the stops I30, and the setting-up coils I38. The sufl'lx letters attached to these reference numerals indicate that the parts thus designated are controlled by keys having letters corresponding to the suffixes. For example, when key B is depressed, it closes switches 50b, 58b, and 10b, and energizes coil I381) to move stop 1301) into operative position toengage the radial arm 96b of condenser shaft 93. In this way it is easy to identify in Fig. 14 the different parts that come into play when a key is depressed. I

Still referring to Fig. 14, it will be seen that the restoring coils I39 are connected in parallel to the two conductors I19 and I802 Conductor I19 is connected to the main lead I16, and conductor I is connected to the switch arm I65. Consequently, whenever the switch lever I8 is thrown from "off to on position, all the coils I39 are energized, and the previously actuated stop I30 is withdrawn to normal inoperative position.

. This restoring circuit is also closed when the circuit. The setting-up coils I38 are connected atone end in parallel to a conductor IBI, which is connected through wire I18 to the side I15 of the supply circuit. The other ends of coils I38 are connected to the key-operated switches 58(L-586 by conductors I82a-I82e, respectively. That is to say, coil I38a is connected by wire IBM to switch 58a; coil I38b is connected by wire I82b to switch 58b; and so on for the other setting-up coils. As explained in connection with Figs. 4, 5, and 6, the individual switches 58 have a common contact .bar 63, which is shownin Fig. 14 as a conductor 63 provided with contact extensions 63 for engagement with the spring fingers that represent the switches 58. The common conductor 63 is connected by a wire I83 to the supply main I16. Consequently, when any one of the keys A -E is pushed down, the

associated switch 58 is closed to connect the in engagement with the common contact bar 63, and from here through wire I83 to the other side I16 of the supply circuit. The circuit through each of the other coils 38 can be traced in like manner when the corresponding key is depressed.

The conductor 68 in Fig. 14 represents diagrammatically the conducting bar 68 of Figs. 4, 5, and 6. It will be remembered that the bar 68 is not only a common support for the switch members 10, but also acts as a common electrical connection for the same. This construction is diagrammatically indicated in .Fig. 14, Where the switch members 1011-102 are electrically connected by wires to the common conductor 68, which in turn is connected to conductor I19 by a wire I84. .the common contact bar 66 of Figs. 4, 5. and 6 is represented. in Fig. 14 by a conductor 66 provided with contact extensions 68' for engagement by the switch members 10a 1Dc. When any one of the switches 10 is closed by a depressed key, the coil 88 is energized to move the bar 1I into locking position. This circuit can be traced as follows: From supply main I through wires I18 and I85 to coil 83, from there through wire I86 to the common contact bar 66, then through the particular switch 10 that was closed by the depressed key, to the common contact bar 68, and finally through wires I84 and I19 to the other side I16 of the supply circuit. No matter which of the switches Hid-10c is closed, the circuit through coil 83 is established through the connections that have just been traced.

ivhen any one of the switches Blitz-58c is closed by the actuation of the associated key through the pivotedlever 39, the circuit through the operating coil H3 is closed through the following connections: From the main lead 115 through wires I18 and I11 to coil II3, thence by wire 54 through the closed switch 50 to the common contact bar 52, through wire 55 to the connecting point I81, and from there through the common return conductor I19 to the other side I16 of the supply circuit. It is thus clear that no matter which one of the key-controlled switches 50a-50e is closed, the coil H3 is ener-- gized to rotate the condenser shaft 93 in the man her previously explained.

I have already mentioned that the function of coil I I4 is to restore the condenser shaft 93 to normal position through the reverse operation of the gear connections I09, I01, I08, and H9. The circuit through restoring coil H4 is automatically closed when the main switch I8 is thrown from on to off position. Let us suppose ihat the switch lever I8 is about midway of either final position and closes the switch arms I63, I65. and I66. The closing of these three "ches automatically energizes the three re- .g coils H4, 84, and I48, respectively. The '1 nit through coil I I4 is established thus: From the lead 215 through wires I18 and I11 to (.Cii I i 4, by wire I88 through the closed switch members l63 and I61, and through wire I89 to the other side I16 of the supply circuit. The energizing of coil II4 rotates the large gear I08 counterclockwise (as viewed in Figs. 11 and 14) until the projection. I23 strikes the fixed stop I24. This does not occur until after the gear I08 has moved the condenser shaft 93 back to normal position through the small gear II 9. It was previously explained that when the large gear I08 is in normal position, it is out of mesh with to normal position.

' position.

the small gear I I9 on shaft 93, so that the latter is free to be turned by hand in the usual way.

The function of coil 84 is to restore the locking bar H to normal or releasing position. It has already been described (see Fig. 3) that, when the coil 84 is energized, the lever 11 shifts the bar H from locking to normal position by bringing the transverse slots 15 of the bar into line with the keys A-E. This restoring operation of bar 1I takes place automatically when the switch arm I8 is thrown from on to "off" position. The circuit through coil 84 is traced as follows: From supply lead I15, through wires I18 'and I85 to coil 84, through wire I90 across the closed switch contacts I68 and I65, through wire I80 to coils I39 in parallel, and thence through return lead I19 to the other side I16 of the supply circuit. For convenience the coil 84 has been connected in series with the coils I39, but it is evident that the circuit through coil 84 may be closed independently of coils I39.

When the main switch I8 closes the switch contacts I68 and I69, coil I48 (see top of Fig. 14) is energized to restore the condenser shaft 93 This particular operation is not necessary when the switch I8 is thrown from on to off position to disconnect the control box from the radio receiver, because the coil II4 restores the condenser shaft to normal position. The practical utility of the restoring mechanism operated by coil I48 resides in the assurance that the condenser shaft will always be in normal position when the operating coil -II3 is energized on the depression of key.

When the switch I8 is moved from oiff to on position to connect the radio set and the .control mechanism with the supply circuit, there is no movement of condenser shaft 93 if the latter is already in normal position. That is so, because under those conditions the switch arm I 55 is out of contact with theterminal strips I53, as shown in Fig. 12. However, should the condenser shaft 93 be out of normal position when the main switch I8 is closed, as may happen if the shaft was previously tuned by hand, the coil I48 is energized to actuate the rack bar I46 and thereby rotate the shaft 93 until the projection I20 The circuit through coil I 48 pressed. For illustration we may select key D.

The first switch to be closed when the key is pushed down is switch 58d, which closes the circuit through setting-up coil I 38d, whereby the stop I380! is moved backward into operative As the key is pushed down farther, the switches 50d and 10d are closed. The switch 50d closes the circuit through the operating coil 'II3, which rotates the condenser shaft 93 until the arm 96d strikes the stop 930d, whereupon the condenser shaft is stopped. When this happens, the radio set is in tune with the wave length on which the selected station broadcasts. As previously explained; the arms 96 on tuning shaft 93 are supposed to be so adjusted as to tune the radio set for the diiferent stations that have been selected when these arms strike he associated guish the different lamps, 1' have indicated them stops. The closing of switch 19d energizes coil 83, which shifts the bar II to locking position, so that the raised keys cannot be pushed down and key D is locked against return movement.

The importance of closing switch 58 in advance of switch 50 when a key is depressed, will now be fully understood. It is necessary that the stop bar 139 be set up by energizing its coil I38 before the operating coil H3 is energized to rotate the condenser shaft 93, so as to make sure that one of the arms 96 will strike the appropriate stop and tune the receiver.

When the operator wants to turn off the set, he throws the switch I8 to off position, whereby the restoring coils 84, IN, and i3 9 are energized to restore, respectively, the locking bar II, the condenser shaft 93, and the actuated'stop B9, to normal position. The coil M8 will also be energized, but at this time it will merely aid the coil ill to turn the condenser shaft backward until the gear I98 passes out of meshwith gear H9. If at that moment the arm H9 on shaft 93 does not engage the stop I, the coil 8 imparts the final movement to the shaft and thereby assures its return to exact normal position. The entire mechanism is now in condition to operate when the next controlling key is actuated. It is thus clear that a person need not do anything more than merely push down a key in order to bring in a selected station on his radio set. The control box K can be located at any convenient place away from the radio cabinet. A person may have the control box before him on a table, or on the arm of a reclining chair, and an invalid may have the box in bed. In other words, wherever a person is comfortably seated or lying down, he can have the control box within easy reach to operate his radio receiver through no greater exertion than pushing down a key. The control box K, which need not be much bigger than a cigar box, can be made as pleasing and artistic in appearance as desired. Of course, the control box could be mounted on the radio cabinet itself, or even made a part thereof, but the greatest advantage of this iiivention' from the standpoint of-convenience resides in the remote control feature.

I have stated that the control box it may be provided with windows it, one for each key, so that when a key is pushed down, the corresponding window is automatically lighted by an electric lamp 89 (see Figs. 1, 5, and 6). Each lamp circuit is controlled by a switch arranged to be automatically closed on the operation of a key. Each of these lamp switches consists of a fixed contact arm i9 3 and a movable contact arm E95, as best shown in Fig. 10. For convenience, these switch arms may be mounted on the channel bar 29, which serves as a guide and support for the keys 29. It is obvious that the lamp switches H t-4% should be insulated from each other. The movable switch arms I95 are in the form of spring fingers terminating in a lateral offset 230i the adjacent key 29 when the latter is pushed down. In other words, when a key .is depressed, the lateral offset 23 pushes the adjacent spring finger i95 against the associated contact i94 to close the circuit of the particular lamp that lights the window back of the depressed key. 1

The circuit connections for controlling the individual lamp circuits are diagrammatically represented in Fig. 14, where the key-controlled lamp switches .l9ll95 are shown for convenience at the right of the drawing. To distinby the reference characters 89a.89e,. to show that lamp 89a is lighted when key A is pushed down, that lamp 8% is lighted by key B, and so on. for the remaining lamps. For the same reason I have differentiated the switch arms I95 by the reference characters l95a-l95e, respectively. The lamps 99 are connected in parallel to conductors i9! and I98, which are connected to the main supply leads H and I16, through wires I99 and 299. If desired, an adjustable resistance 2M may be inserted in the lamp circuit to regulate the voltage at which the lamps are fed. All the lamps are normally out of circuit. When a key is depressed, the corresponding switch 95 is closed and the lamp controlled by that switch is lighted. The lamp remains lighted until the key returns to normal position. It should be noted that the lamp circuit remains closed even after the depressed key has moved slightly npward before it is locked by the bar II, as illus trated in Fig. 6. It is only when a depressed key is thrown up to normal position by the spring 44 that the lamp is extinguished. This notifies the operator visually that the control box is disconnected from the radio receiver.

The modification of Fig. 15 differs from the system of Fig. l i mainly in employing an electric motor to operate the condenser shaft 93 instead of the solenoid driving mechanism previously described. The condenser shaft 93 of Fig. 15 carries at one end a magnetic armature 202 adapted to cooperate with a pair of electromagnets 203, which are energized by coils 2M. The electro magnets 293 product a 4-po1e field in which the pole pieces are arranged along two diameters at right angles to each other. Thearmature 292 is in the form of a cross whose arms register with the pole pieces of the field. The electro-rriagnets 2%, which I shall hereafter call'tiie field magnet, are rigidly mounted on a rotary shaft in any practical way. Since Fig. 15 is intended to show the parts in diagrammatic outhne only, for the sake of cl'earness, I have indicated the mounting of the field magnet 293,021 shaft Edi; by rods 2%, which connect the field members tilt with a 2t"! fixed on the'shaft. In actual practice, the field magnet 293 would be mounted directly on the non-magnetic disk 291, and the spacing rods wt-have been put in to permit a clear illustration "of the other parts. The magnet coilstii i are connested in series to a pair of collector rings 2% by wires 299 and no. A pair of brushes 2! I and M2 engage the contact'rings 298 to keep the sin cult closed through the coils 29 3 during the rotation of shaft 205. An electric motor 2l3 has a. shaft 2 carrying a pinion 2l5 arranged in perend of shaft 295, which is therefore connected. to the motor in reduced transmission ratio. It

is hardly necessary to explain that the gears 265 and M6 as outlined in Fig. 15 are not intended to indicate the correct gear reduction between shafts 2M and 295, but represent any practical manent mesh with a gear wheel 216 fixed on the g still be running. The circuit of the magnet coils 204 is controlled by two sets of switches 2II and 220. The individual switches of the first set are marked 2IIa to 2I'Ie, and the individual switches of the second set are marked 225a to 2256. For convenience, these two sets of switches may be referred to as a group by the reference numerals 2I'I and 225, respectively, and I have used the sumx letters a-e to indicate the association of these switches with the control keys A-E. The switches 2| I comprise each a pair of normally open contact arms, one oi. which (marked 2I8) is connected to the associated switch arm 50 by an insulating pin 2I9, or in any other practical way. It is clear from Fig. 15 that when a key is depressed, the rear end oi! lever 39 not only closes the switch 50, but also the connected switch 2II. The spring arms 2I8 of the switches 2II are connected in parallel to a common contact bar or conductor 2I9. The other terminals of switches 2I'I are connected in parallel to a common conductor 222, which is connected by wires 223 and 224 to collector brush 2.

The otherswitches 225d-225e for controlling the circuit of the magnet coils 204 are mounted on the adjustable stops I30. Since these mountings are alike, a description of one will be sufficient. Referring to Figs. 17 and 18, each stop I20 carries an insulating block 226 on which are mounted two contact arms 221 and 228. Each pair of these arms constitutes a switch 225. The arm 22B is in the form of a spring finger normally in contact with arm 22! and carrying at its free end an insulating pin 229, which projects through a hole 230 in the stop I30. When the associated arm 96 on condenser shaft 93 strikes the projecting pin 229, the spring finger 228 is forced out of engagement with arm 22? and the switch is opened. This happens just before the arm 226 strikes the actuated stop I30 to hold the condenser shaft in tuning position. The spring fingers 228 also act to some extent like buffers or shock-absorbers for the arms 96. The switches 225 are connected in series to a conductor 23I, which is shown in Fig. 15 as a line divided into sections connected by the normally closed arms 221 and 228 of switches 225. The conductor 23I is connected by awire232 to the common conductor 2!!! of the switches 2Il. Although the switches 225 (contact arms Ml and 22B) are normally closed. the circuit through the magnetizing coils 204 is not completed until. one of the switches 2I'I is closed by op the corresponding key. For example, wh D is pushed down, the circuit through coils tilol is closed through the following connections: From supply lead 22I through wire 2% to col." lector brush 2I2, through wire Lilli, coils 2% in series, wire 209, collector brush till, through wires 224 and 223 to the common conductor 222, through closed switch 2 I10! to point 234 through wire 2 I8 to conductor 23I and the closed switches 225 in series, through wire 220 to point 233, and through conductor 231 to the other side of the supply circuit. No matter which. key is operated, the circuit through the coils 204 is traced in the same way. Although the circuit of coils 204 is broken before the arm actually strikes the setup stop I30, the pin 229 projects so slightly above the stop that the momentum of the moving parts carries the arm 96 against the stop into correct tuning position.

The circuit of motor 2I3 in Fig. iii is controlled by the switches 50. It has already been explained that the switches 50 are no mahy open .the condenser shaft 93.

and are closed individually by the key-operated levers 39. To trace the motor circuit let us sup-- pose that key D has been actuated. From the supply main 22I we go through wire 238 to'the motor windings, from there through wire 238 to point 240 of the common contact bar 48, through the closed switch 50d, then through the common contact bar 52 to point MI, and through wire 242 to the return lead 231. It is seen from this that the motor 2 I3 and the clutch coils 204 are connected in parallel, that each of these parallel branches goes through the switches 50, and that the circuit of coils 204 goes through the switches 225 in series. Consequently, when any one of these series switches is opened by the corresponding arm 96 striking the actuated stop I30, as previously explained, the clutch circuit is broken and the tuning shaft 93 is stopped, even if the motor 2I3 should still be running. In other words, after a key has been pushed down to close the switches 50 and 2Il, it makes no difference how long the operator holds the key depressed, because the clutch circuit is automatically opened when one of the arms 96 encounters the actuated stop I30'. It takes only a fraction ofa second for the motor to turn the condenser shaft into tuning position, so that a person need not hold down an actuated key any longer than is necessary for him to feel that the key has been fully pushed down. If desired, the motor circuit can be led through the series switches 225, so that the opening of any one of these switches simultaneously deenergizes the clutch coils 204 and stops the motor.

Attention is called to the fact that the system of Fig. 15 requires no restoring mechanism for It is immaterial in what position this shaft is left when the switch I8 is thrown off. When a control key is depressed, the shaft 93 is rotated until stopped by the actuated stop lilll, irrespective of what position the shaft previously occupied. In this respect, the system of Fig. 15 is simpler than that of Fig. 14. Furthermore, the motor drive of Fig. 15 is preferable to the solenoid drive of Fig. 14. The main switch I8 in Fig. 15 includes only two sets of contacts, as compared with the four sets of contacts in Fig. M. The switch Ill connects the radio set to the supply circuit, the same in Fig. M. The other switch operated by lev comprises a spring finger contac' her The restoring coil t l, which shifts spring finger tact member d to a conductor Ml, which forms a c ion connection for one side of the restoring c These coils are there :iore connected in p... a1. e1 to conductors 2% and 24l, and the circuit is closed through all these cells whenever the switch members 2 and M5 are brought into contact by the toggle lever it. Otherwise, what has been said about the opcratlon of Fig. lei applies to Fig. 15 without the need of repetition. For this reason it have used the same reference characters to indicate like in these two systems.

In i -lg. 15, the circuit oi. motor H3 and the circuit of the magnetic clutch coils 204 are com nectetl in parallel. These connections may be so changed that the motor 2I3 and coils 204 are r connected in series, and the switches 22?: connected in parallel with each other. This moth-- fioation, which is diagrammatically indicated in Fig. 16, is simpler than the system of Fig. 15 to the extent that the switches 2Il can be omitted. It is clear from Fig. 16 that, when any one of the key-controlled switches 50 is closed, the circuit is completed through the motor 213 and the magnetic clutch coils 204, until the arm 98 on the condenser shaft strikes the actuated stop I30 and opens the corresponding switch 225.

In a preferred embodiment of the automatic tuning system illustrated in Fig. 15, I provide means to inform the operator when the condenser shaft has reached tuning position. For

this purpose I make use of the lamps 88, which are behind the windows I9, and so connect them in circuit that the lamp associated with an actuated key is not lighted until the condenser shaft is in correct tuning position. In Fig. 15, the lamps 88 are connected in parallel in a circult represented by conductors 248 and 249 which lead to a battery 250, or other source of power. In practice, the lamp circuit will be connected to the plug H3; but 'I have"indicated a separate source oi. current 250, in order to simplify the circuit diagram. In Fig. 15, as in Fig. 14, the lamps 89 are individually distinguished by sufiix letters to indicate the corresponding keys with which the lamps are associated. Referring to Figs. 17 and 18, it will be seen that the insulating block 226 of each stop 130 carries a pair of switch contacts 256 and 252, which maybe spring fingers normally held apart by inherent tension to keep the lamp circuit-open. The spring finger 25i carries at its free end an insulating projection 253 arranged to be engaged by the switch arm 228 when the latter is pushed down by the arm 96. This actuation of member 288 moves it into contact with member 252 to close the branch circuit of the-associated lamp. As seen in Fig. 15, the lamps are controlled individually through the parallel branch circuits 2M, and each oi these circuits is controlled by the switch member on the corresponding stop ltd. Norinally, the lamps are unlighted, because their respective branch circuits are all open. Let us now say that key A is pushed down. As soon as the arm the on condenser shalt 85.3 strikes the projection on the set-up stop itiic, the ssscc'i" ated switch arm 525i isclosed and lamp 8912 is lighted. The operator is now informed that the condenser shalt has reached tuning position, so that it issafe to release the depressed hey.

Fig. 19 illustrates diagrammatically another embodiment oi my invention, in which the condenser shait iii] is driven by the electric motor Elli through a slip clutch. Perhaps the simplest form oi a clutch oi that kind comprises a spring belt 255 running over a small pulley 256 on the motor shaft and a larger pulley 251 on the condenser shaft. The belt 255, which is here as sumed to consist of a wire coil spring, is sumciently tensioned to drive the condenser shaft when the motor circuit is closed until one of the arms ildstrlkes the set-up stop. "ll. The con denser shaft is now stopped, even it the motor shaft should continue to rotate, because the spring belt 256 will slip in one or both of the pulleys 256 and till. the motor circuit is controlled by the key-operated'switches W, which are normally open. When any one of these switches is closed, the motor circuit is completed through the following connections. From supply main 22! to wire 23!, through the motor windings and wire 238 to point 239', then through the common contact bar #8, from there through the closed switch 59 to the common conductor 52, and from there by wire 25! to the return lead 231. II-deslred, the switches 22! of Fig.

may also be used in'the system of Fig. 19, but I have omitted them to avoid needless repetition. Otherwise, what has been said about the operation of Figs. 14 and 15 applies to Fig. 19. The motor circuit of Fig. 15 and Fig. 19' may include a. rheostat 259 to regulate the current as required.

In the remote-control tuning systems of Figs. 14, 15, and 19, the various electromagnetic devices are automatically cut out of circuit after performing their intended functions, so that no current is consumed during the operation otthe receiver. Thus, when a depressed key is released, it is raised by spring 44 sufllciently to open the switches 50, 58, and 10 (see Fig. 6), whereby the circuits through coils H3, I38, and 83, respectively, are broken. In Fig. 15, the magnetic clutch coils I01 are automatically cut out of circuit by the opening of switch 225 when the condenser shaft is in tuning position, and the circuit of the driving motor H3 is interrupted when the operator releases the depressed key of the control box. As for the restoring coils 84 and H9 in Figs. l4, l5, and 19, and the restoring coils H4 and MB in Fig. 14, these circuits are closed only when the switch lever [8 passes from on to oil position or vice versa. Consequently, the automatic tuningapparatus of my invention requires very little consumption of cur.- rent, being in circuit only for a few seconds when a key is depressed and when the main switch i8 is thrown off. This advantage of economy is of practical importance. Of course, one of the indicating lamps til is alight during the operation of the receiver, but these small lamps consume a neglible amount of current, and moreover they can be omitted.

y In some or" the constructions that have been described, or that may be devised by others within the scope or this inventior 'it is possible that the arms so may strike the set-up stops Hill with such force as to rebound and thereby throw the condenser shaft out of correct tuning position.

-To prevent the possibility of this happening, I

provide positive locking means between the stops Hill and the tuning arms whereby the latter are automatically loclred to the set-up stops to assure the correct position of the condenser shaft. This automatic locking means may be carried out in various ways, one of which is illustrated as an example in Figs. -22. Each arm 98 carries at its free end a head 250 on which is mounted a U-shaped spring latch consisting of a pair of fingers 28! shaped to form locking shoulders 26?. minate in diverging extensions 263. The spring latch 281 is connected to the head 260 in any practical way, as by a screw or rivet {64. When the arm 9% approaches the set-up stop bar I30, the latter spreads the spring fingers 2M by passing between the beveled extensions283. As soon as the arm 98 strikes the stop bar W), the shoulders 262 of spring latch 28! snap under the bar and positively lock the arm against reverse movement.- In other words, when the condenser shaft reaches its intended tuning position, it becomes automa ically locked in that position until the stop bar Hill is withdrawn during the restoring operation. To facilitate-the cam action between the stop bar I30 and the diverging extensions 263, the sides of the bar may be beveled, as indicated at 265 in Fig. 22. This automatic locking feature may be considered as applied to the tuning arms "in all the embodiments herein de- The free ends of the latch fingers 26i ter- I speak of tuning s scribed, but for simplicity and clearness in the drawings, this particular feature has not been illustrated in the assembly views.

' Instead of providing the control box K with windows II, to be illuminated when the corresponding keys are pushed down, I may provide the keys themselves with lamps and transparent bottom of cup 261, and the terminals of this socket are connected to conductors 289, which pass through the hollow stem 266. The socket 268 is adapted to receive a small electric light bulb 210. The upper end of cup 261 is closed by a cap 2' of transparent or translucent material, such as celluloid, oiled paper, glass, isinglass, etc. The cap 21! is supposed to have written or printed thereon appropriate marks for identifying a selected station. The cylindrical flange 212 of cap 211 is sufficiently springy to grip the cup 261 in a tight fit and yet permit removal of the cap when desired. It is self evident that the cap 21! should be sufficiently strong to withstand the pressure of the finger when the key is pushed down. The lamp 210 may be lighted continuously after the main switch l8 has been thrown on, but it is preferable to utilize the lamp circuit control described in connection with Figs. 14 and 15, where a lamp is lighted only when a key has been pushed down. The illuminated key is a constant reminder to the operator that the radio set is tuned to a certain station. When the control'box K is provided with a set of self--lighting keys, such as I have just described, the light transmitting caps 21! may be of different colors to emphasize the optical effects of the lighted keys.

Although I have shown and described certain specific constructions, I want it understood that the various features of my invention may be embodied in other ways than herein set forth by way of example. It is to be expected that, when engineers undertake to build automatic radio receivers in accordance with this invention, they will. resort to change their particular re without departing tion as defined in tl necessarily mean. a b on which the elements are mounted, but include any that controls the position or condition o tuning means with which the receiver is provi I claim as my invention:

1. The combination of a radio receiver having a tuning shaft, electromagnetic ineclila operating said shaft, mechanical mean tively stopping said shaft in a 131'. position, electromagnetic means adapted energized to render said shaft-stop ing 1 operative, means for ale-energizing said elc magnetic means after the shaft is stopped in sired tuning position, means for automat ,ly' tie-energizing said electromagnetic opei ting mechanism in response to the stopping of the shaft, means for locking the stopped shaft against rebound, means whereby the operative condition of said locking means is not affected by the de energizing of said electromagnetic means, and

manually controlled means for releasing the locking means.

2. The combination of tuning means for a radio receiver, electromagnetic mechanism for operat ing said tuning means predetermined amounts to bring in any one of certain broadcasting stations, an electric control device having a set of manually operable members representing said stations, connections controlled by said members to cause said mechanism to automatically operate said tuning means to bring in the station represented by the actuated member, a normally open switch associated with each member and arranged to be closed by the movement of said member to tuning position, a signal lamp mount ed adjacent each member and controlled by the associated switch, whereby the operation of any member automatically lights the adjacent lamp, and means for preventing operation of another key as long as the lamp of a previously actuated key remains lighted.

3. In combination with a radio receiver having a tuning shaft operated by an electric motor, a series of selectively controllable devices representing each a station, means whereby each device is adapted to stop the shaft and open the vices, connections for closing the motor circuit when any key is operated, means for locking an actuated key against return to normal position, said locking means also locking the other keys against operation, and a manually operable member separate from said keys for moving said locking means to releasing position.

i. The combination of a radio receiver having a tuning shaft, means for operating said shaft, a series of'electromagnetic devices arranged longitudinally of said shaft, each device representing a certain station, a movable member operated by each device when the latter is energized, a plurality of arms mounted on said shaft in different angular positions and axially spaced, so that each arm is in line with one of said members and engages the same when the latter is in actuated position, whereby the shaft is positively held in selected tuning position, a series of keys for se lectively energizing said devices, an electric lamp associated with each key, a normally open switch b circuit of each and means for one y closing the switch of the correspondit when an actuated member is gned arm, whereby the lamp is automatically lighted when i is tuned in. combination of a radio receiver having shaft, a projection on said an jection, means for operating said shaft, and for automatically locking said pro j ctioi'i to said stop i /hen these parts engage each said locking means permitting Withdrawal aid stop from the path of said projection.

In a radio receiving system, the combination of a tuning shaft, an electric motor for opcrating said shaft, an adjustable stop for controlling the movement of said shaft, means on said shaft to engage said stop when the latter is in operative position, said stop and means cooperating to arrest the movement of said shaft in a direct mechanical way, and means for automatically breaking the motor circuit in response tothe stopping of the shaft by said stop, said last mentioned means including a switch element ill movably mounted on said stop and actuated by said means on the shaft.

7. The combination of tuning means for a radio receiver, electromagnetic mechanism for operating said tuning means predetermined amounts to bring in any one of certain broadcasting stations, an electric control device having a set of manually operable keys representing said,

stops representing each a certain broadcasting.

station, a corresponding plurality of means on said shaft adapted. each to engage one of said stops to limit the movement of the shaft, said stops being normally out of the path of travel of said engaging means and being substantially immovable when struck by said means, whereby the tuning shaft is stopped in a direct mechanical way, key-controlled electromagnetic mechanism for selectively operating said stops, and switch means carried by each stop and movable independently thereof to break the circuit of said clutch in response tothe shaft striking the selected stop, said tuning shaft being always free to be manually operated.

9. The combination with a radio cabinet containing a rotary tuning shaft, electromagnetic apparatus for operating said shaft and a plurality of electromagnetic devices selectively controlled to limit the rotation of said shaft through a predetermined angle, of an electric control box separate from said cabinet and usable at a, distance therefrom, a set of keys carried by said box, each key representing a. selected station, switch mechanism insaid box controlled by each key to operate one of said electromagnetic devices and thereby limit the rotation of said shaft to tune in the station represented by the actuated key, means whereby the operation of'any key energizes said electromagnetic apparatus to actuate the tuning shaft, a signal lamp in said box for each key, these lamps being normally unlighted, circuit connections automatically controlled by the movement of any key to station-selecting position for lighting the signal lamp of the actuated key, and means for preventing operation of another key as long as the lamp of a previously actuated key remains lighted.

.10. The combination of a radio receiver having a rotary tuning shaft provided with radial arms axially spaced on the shaft and arranged in predetermined angular relation, each arm representing a selected'station, a series of movable stops associated with said arms and normally out of the path of movement of said arms, electromagnetic means associated with each stop to move the same into and out of the path of the particular arm controlied by that stop, said stops being substantially immovable when struck by said arms,

so that each stop positively limits the rotation of said shaft through a predetermined angle, electromagnetic mechanism for operating said shaft, means automatically operable in. response to the engagement of any one of'said arms with the associated stop for locking the stopped shaft against rebound, electric connections for energizingthe electromagnetic means of each stop to move the same into the path of the corresponding arm on said shaft, a series of manually operated members for selectively actuating any stop to bring in the desired station, and means for automatically stopping the operation of said mechanism when a desired station is in tune.

11. A remote tuning device for radio receivers in which the tuning shaft is operated by electromagnetic mechanism, said device comprising a portable box provided with a series of depressible keys, each key representing a selected station, normally open switch means in said box closed by each key when the latter is depressed to control said mechanism, means'for looking a depressed key against return to normal position, a switch carried by said box for turning the receiver on and 01f, and means controlled by said switch for releasing the locked key.

12. A remote control device for radio receivers comprising a series of keys representing each a station, switch means associated with each key for closing the circuit of an electric motor which drives the tuning shaft of the receiver, means for automatically locking an actuated key against preventing operation of the other keys, and elec tromagnetic means for rendering said locking means ineffective. 1

13. A radio receiver having variable tuning elements normally unbiased to any position, means for operating said elements, other means for locking said elements in selected tuning position, said locking means including a movable part adapted to remain in looking position without attention by the operator, and electromagnetic means for moving said part to releasing position.

14. A radio receiver having an adjustable tuning member normally unbiased to any position, means for operating said member, other means for stopping said member in selected tuning positlon, said stopping means automatically locking said member when it stops, said locking means including a movable part adapted to remain in looking position without attention by the operator, and electromagnetic means for moving said part to releasing position.

15. The combination 01 a radio tuning shaft having an arm, a stop movable into and out of the path of said arm,'and means for automatically locking said arm to said stop when these parts engage, whereby the shaft is locked in tuning position.

16. The combination of a radio tuning shaft, a slidable bar mounted to move at right angles to said shaft, means on said shaft adapted to engage said bar when the latter is in operative position for stopping the movement of said shaft,

a pivoted member connected to said bar for actuating the latter in both directions, electromagnetic means for. rocking said member in one direction, and other electromagnetic means for rocking said member in the other direction.

17. In a radio receiver, the combination of a rotary shaft for operating a variable tuning device, a member carried by said shaft and rotatable therewith, a stop movable into and out of the path of said member, and means for automatically locking said member to said stop when these parts engage.

18. In a radio receiver, the combination of a rotary shaft for operating a variable tuning device, a plurality of stops movable into and out of operative position, means for selectively conreturn to normal position, said locking means also trolling said stops individually, and means carried by said shaft and adapted to become locked to any stop in operative position.

19. A radio receiver having a rotary tuning shaft and mechanism for operating said shaft to desired tuning position, in combination with a set of keys forcontrolling said mechanism to stop said shaft in tuning position for a preselected station, means whereby any actuated itey is locked against return to normal position, a switch for turning the electric power for said receiver on and off, and means automatically controlled by the opening of said switch for releasing a locked key.

20. A radio receiver having a tuning shaft and electromagnetic mechanism for operating the same to preselected positions, said receiver having a manually operable switch for turning the electric power on and off, in combination with a set of push buttons representing certain stations, electric connections between said push buttons and said mechanism for controlling the latter to tune in the station represented by an actuated push button, means for automatically locking any actuated push button against return to normal position, said locking means also looking the oth er push buttons against actuation, electromagnetic means for operating said locking means to releasing position, and connections for energizing said releasing means when said main power switch is closed.

21. In a radio receiver, the combination of a rotary shaft operable for tuning said receiver, means for actuating said shaft; a plurality of independently movable stops representing each a certain station, an electromagnetic device associated with each stop for actuating the same to stopping position, means whereby any stop remains in stopping position when the associated device is de-energized, selectively operable means for energizing any one of said devices, means movable with said shaft for enaging an actuated stop and thereby arresting further rotation of the shaft, and electromagnetic means adapted when energized to restore any actuated stop to normal inoperative position, said restoring means being independent of said devices.

22. In a radio receiver, the combination of a switch for turning the electric power for the receiver on and off, a rotary tuning shaft adapted to occupy a normal predetermined position, an electric device for actuating said shaft in one direction from normal position to tune in a desired station, manually controlled means for stopping said shaft in preselected position, a second electric device for actuating said shaftin the reverse direction back to normal :position, and means for energizing said second device when said main power switch is closed.

23. A radio receiver provided with an adjustable tuning member, means for locking said member in preselected tuning position, a switch for turning the electric power for said receiver on and off, and means controlled by said switch for releasing the locked tuning member.

24, In tuning apparatus for a radio receiver, the combination of a rotary tuning shaft, means for operating said shaft, a set of individually movable stops normally inoperative in relation to said shaft, each stop representing a certain station, a plurality of selectively operable means for moving any desired stop into operative position to arrest said shaft in preselected tuning position, switch mechanism for turning the electric power for said receiver on and oil, a flnge piece for operating said switch, and mea omatically controlled by the opera: finger piece for moving apreviou stop back to normal inoperative tion.

25. A radio receiver provided with a switch for turning the electric power on and off, said switch comprising a movable finger piece, a rotary tuning shaft, electric mechanism for operating said shaft to preselected tuning positions, said mechanism including. a series of individually controllable members for stopping the shaf t in predetermined position, a pair of electromagnetic coils associated with each member for moving the same into and out of operative position respectively, each pair of said coils comprising a stopping coil and a releasing coil, a set oi push. buttons for individually controlling the circuits of the stopping coils, and switch connections controlled by said finger piece for energizing the releasing coils when said power switch is closed.

26. The combination of a radio receiver hav ing a tuning shaft, electromagnetic mechanism for operating'said shaftto bring in any one of a series of broadcasting stations, an electric con,- trol box having a series of push buttons representing said stations, connections controlled by said push buttons for energizing said mechanism to rotate said shaft until the station represented by the actuated push button is in tune, a series of signal lamps in said box, there being a lamp for each push button, a series of normally open switches mounted in said box and arranged to be actuated by said push buttons, whereby the operation of any push button automatically lights the. associated lamp, which stays lighted as long as the corresponding station remains in tune, and means for preventing the operation of another push button as long as the lamp of a previously actuated button remains lighted.

27. A radio receiver having a rotary tuning shaft, an electric motor normally disconnected from said shaft, an electromagnetic clutch for coupling the motor to said shaft, 9. set of normally closed switches connected in paralleh energized when the normally closed switch. in

series with the closed push button switch is opened by the tuning shaft.

28. The combination of radio tuning mecha nism having movable elements operated by a common shaft which is normally unbiased to any angular position, with mechanism for con" trolling the movement of said shaft comprising i F a second shaft, an electric motor for operating said second shaft, connections between said shafts for rotating the first shaft in alternately opposite directions through a predetermined arc, said connections including means for automatically preventing rotation of the first shaft beyond either end of its definite arc of travel, means arranged for movement with one of said shafts, normally inoperative means adapted for engaging with said last-mentioned means to 

